This invention relates generally to the field of systems, instrumentation and methodology for the fixation or fusing of vertebrae relative to each other, and more particularly relates to such systems, instrumentation and methodology that utilize pedicle screws affixed to vertebral pedicles and one or more rods that rigidly connect the pedicle screws of plural vertebrae. Even more particularly, the invention relates to such systems, instrumentation and methodology that utilize a guide wire inserted through the pedicle screws as a means to guide and locate a fixation or stabilization rod through the pedicle screws.
Traditional surgical techniques for affixing rods to vertebrae entail the creation of relatively long incisions to provide access to the vertebrae. Large bands of back muscles are stripped and pulled free from the spine (i.e., retracted) to provide access to the vertebrae. Newer techniques utilize single or multiple short or stab percutaneous incisions at chosen locations rather than a single long incision, with tubular cannulas being inserted to provide access pathways to the vertebrae. Such techniques are often referred to as minimally invasive surgery (MIS). The MIS techniques are preferable with regard to recovery time, since muscle retraction, muscle stripping and the like are minimized or obviated.
The relevant MIS technique for stabilizing the spine involves the insertion of pedicle screws into the vertebral pedicles. A pedicle is the strong, cylindrical, anatomic bridge between the dorsal spine elements and the vertebral body, and is comprised of a strong shell of cortical bone and a core of cancellous bone. Each vertebra has two pedicles and these provide a sturdy base to securely receive the threaded shaft of a pedicle screw. The pedicle screw may be a rigid member, but most preferably comprises a slotted, rod-receiving head mounted in a swiveling or rotating manner to a threaded shaft, such as for example by the use of a ball and socket-type connection. Such screw structures provide greater latitude in connecting the fixation rod and are well known in the art. Spinal fixation or fusion is accomplished by inserting pedicle screws into multiple vertebrae and connecting the screws to each other with a rigid rod secured to the receiving heads of the screws, thereby stabilizing the vertebrae.
In one MIS technique, a relatively small incision is made through the back to expose the vertebrae and pedicle screws are affixed to the pedicles of adjoining vertebrae using cannulated or tubular sleeve extenders. The rod is then transversely passed down through the sleeve extenders, laid into the slots of the receiving heads of the screws and secured using the set screws of the receiving heads, typically externally threaded members received by the internally threaded receiving heads. The rod joins all the pedicle screws and therefore the vertebrae in a fixed and rigid manner. Because the rod is inserted in a non-axial direction, there is still excessive damage to the muscles and other tissue because a slit must be provided, and recovery time is lengthened and healing pain is increased.
In another MIS technique, one or more short incisions or stab incisions are utilized for insertion of the pedicle screws. An example of this system is described in U.S. Pat. No. 7,188,626, issued Mar. 13, 2007 to Foley et al., the disclosure of which is incorporated herein by reference. In this technique, the sleeve extenders are joined and secured, and a swinging rod inserter is connected to this assembly of extenders. The rod inserter delivers a rod through the skin and tissue in an arced pathway and into the receiving heads of the pedicle screws. A problem with this system is that the pedicle screws are often not aligned in a linear manner and may also vary in height. The more out of alignment the receiving heads are, the more difficulty there is in using the swinging rod inserter to deliver the rod. Another problem with this system is that the rod is not restrained or guided along the insertion path in and between the pedicle screws.
In still another MIS technique, a guide wire, suture, cable or similar flexible member is first passed down through a sleeve extender and then through the pedicle screws. The leading end of the guide wire is then passed out through the last sleeve extender or through another incision. Examples of this technique are described in U.S. Pat. No. 6,821,277, issued Nov. 23, 2004 to Teitelbaum, and in U.S. Patent Application Publication No. 2008/0015582, published Jan. 17, 2008 in the name of DiPoto et al., the disclosure of both being incorporated herein by reference.
In our pending patent application Ser. No. 12/315,546, the disclosure of which is incorporated herein by reference, an improved MIS system is provided, the system having a guide wire, suture, cable or similar flexible member as part of a spinal fixation MIS procedure, the guide wire being connected to a collar member for ready mounting onto a pedicle screw. With the guide wire affixed to a first pedicle screw, the free end of the guide wire is passed through the remaining pedicle screws and out of the patient. A fixation rod is then connected to the free end of the guide wire and pulled into position in the pedicle screws.
It is an object of this invention to provide an improved MIS apparatus and methodology for insertion and positioning of the fixation rod in the pedicle screws. It is an object to provide a methodology whereby an interior portion of the guide wire rather than a free end is pulled through the pedicle screws, such that a guide wire loop is presented for connection to the fixation rod. It is an object to provide an apparatus and methodology whereby a malleable template rod is first inserted into the pedicle screws, the malleable rod then being bent to identify the proper configuration for alignment with the pedicle screws, the properly configured malleable rod then being removed from the patient, the permanent fixation rod then being bent to conform to the configuration of the malleable rod prior to insertion and fixation to the pedicle screws. It is an object to provide an apparatus whereby the proper length for the permanent fixation rod is determined by measurements taken of the guide wire or the malleable rod. It is an object to provide an apparatus and methodology enabling alignment of the pedicle screws by positioning the fixation rod in the pedicle screws, manipulating the rod and/or affixing the rod to one of the pedicle screws and then manipulating the rod to properly align an adjacent pedicle screw, affixing the rod to this pedicle screw, and continuing the process.